feat(lsp): add ESLint language server support

[amondnet]

Summary

Add ESLint Language Server Protocol support to the @pleaseai/code-lsp package, enabling real-time ESLint diagnostics for JavaScript/TypeScript files.

Approach

Download and build vscode-eslint from GitHub (following opencode reference implementation):

• Download vscode-eslint from GitHub main branch
• Run npm install && npm run compile to build
• Install to ~/.cache/dora/eslint-lsp/vscode-eslint/
• Server path: vscode-eslint/server/out/eslintServer.js

Technical Details

• Prerequisite check: Only start if eslint is installed in the project
• Root detection: Lock files (package-lock.json, bun.lock, yarn.lock, pnpm-lock.yaml)
• Extensions: .ts, .tsx, .js, .jsx, .mjs, .cjs, .mts, .cts, .vue
• Memory: Uses --max-old-space-size=8192 for large codebases

Tasks

• T001 [P] Add getEslintResourcesDir function
• T002 [P] Add setupEslintDependencies function (download + build)
• T003 Add EslintServer definition with prerequisite check (depends on T001, T002)
• T004 Add EslintServer to LSP_SERVERS array (depends on T003)
• T005 Export EslintServer from index.ts (depends on T003)
• T006 Update CLAUDE.md documentation
• T007 [P] Add EslintServer unit tests

Reference

Based on opencode implementation: ref/opencode/packages/opencode/src/lsp/server.ts (ESLint: Info)